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HLR routing based on IMSI

I am new to this forum but appreciate all the quality information and knowledge from members. I am hoping there is someone out there that can help me with a question I have regarding a project I am currently working on. I am looking to understand how HLRs are identified on SS7 routing network, based on the IMSIs the store.

At a high level the project I am working on is the interconnection of an external HLR (lets call it HLRx) into an existing operators network.

As I understand it this HLRx will need to appear as a new network element within the operators existing SS7 network (ie have its own GT address for signaling routing). But this HLR will contain subscriber information for a subset of the operators IMSIs range (we are an MVNO, integrating our own HLR, and using an sub-range of the operators IMSI range) i.e sub-range could be:
40468 5500000000 to
40468 5599999999

So during the LU procedure (or any call setup procedure) the operators signaling network will need to address HLRx's GT for this sub-range of IMSIs, so as to retrieve subscriber information. Can someone please inform me how this is achieved? Is it that this sub-range if IMSIs is held in a reference table maintained within SCCP GT Tables for example?

I hope I have explained my situation accurately, any help would be greatly appreciated!

Thank you very much for your reply, and sorry its been a while since I posted, but I was hoping you could help with some clarifications?

I am familiar with the MGT addressing and routing for normal roaming scenarios, but our scenario will be slightly different, and perhaps I can try to explain it in a different way.

We will sell our service & SIM card in France for example, this SIM will have multiple IMSIs ie France SFR, T-Mobile UK, Vodafone NL etc up to 8 IMSIs, and one master roaming IMSI profile for any countries outside these where the subscriber might roam to. The subscribers profile and SIM data (for all IMSIs), will be loaded into our HLR located in France. When a customer travels from France to the UK, selection rules on the SIM will ensure that the T-Mobile IMSI is passed to the network based on the MCC+ MNC, so this means that the T-Mobile network will view the IMSI as a local subscriber, however his subscription data is not held on a T-Mobile's HLR, it is held on our HLR located in France. So in this scenario the standard MGT translation & routing will not work, because the IMSI is seen as a local to the T-Mobile network, the issue is that the T-Mobile network will need to identify that this IMSIs subscription data is held in our HLR, and route messages to the correct location, otherwise this IMSI will not be able to authenticate to the T-Mobile network.

I am guessing that our HLR will need to appear in T-Mobile's network as another HLR within their network, with its own point code?

Any additional feedback on this approach would be greatly appreciated, and specifically any information or thoughts relating to the configuration that would be necessary on the SCCP to facilitate this kind of routing based on a subrange of IMSIs, would be great?